Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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081 FXUS65 KGJT 070900 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 300 AM MDT Fri Jun 7 2024 .KEY MESSAGES... - Hot conditions expected again today with a few triple digit readings in the lower desert valleys...most areas will be 10 to 15 degrees above normal. - Thunderstorms develop this afternoon as moisture begins a push back into the region. A few storms will produce strong outflow gusts. - Low valleys remain warm and dry, while afternoon mountain showers and thunderstorms remain a threat into the early half of next week. && .SHORT TERM /THROUGH SATURDAY/... Issued at 300 AM MDT Fri Jun 7 2024 There is probably no better indicator that a push of moisture is underway that having ACCAS showing up on the radar during the early morning hours. This moisture on top of the deep EML will help aid an uptick in thunderstorm development today. Getting this moisture to the ground as precipitation is another matter and this looks more likely to happen across the northern CWA today where low level moisture has been pooling...possibly from the help of hydrology. Another meteorological cool happening is the moisture being forced over the southern divide in NM as a front backs up along the lee of the Rockies. Dewpoints in the teens are now in the upper 40s near ABQ and this moisture will get advected into our southern CWA this morning. Models suggest this southern moisture source being mixed out through the day...and though it will aid in the elevated formation of convection the hot dry airmass should win out with virga and possible gusty winds being the main threat. Farther north the low level moisture profile and upper level wind profile suggest better storm organization and moderate to heavy rainfall rates and gusty winds stand a better chance of getting to the surface. Most of this activity should wane by sunset but an well defined wave currently upstream of us in W.NV will be moving through late tonight. This will likely keep some isolated showers/storms going closer to the WY border overnight with the subsidence in the wake of the shear zone providing somewhat of a stronger cap to overcome on Saturday across our southern CWA. Terrain forcing...left over boundaries and residual moisture will favor storm formation again mainly across the northern half of the CWA later in the day with most of the CAMS firing storm on the high plateaus and Uintas by early afternoon. Overall both instability and shear look weaker but after a few storm generations some of this activity should spread to adjacent valleys before sunset. Hot temperatures are expected again today but the added moisture has trended most guidance downward compared to a few days ago. Still expect triple digits over some of the lower desert/red rock country with a drop across the board of about 3 to 5 degrees on Saturday. This warm temperature continues to take it`s toll on the snowpack and many river systems will continue to rise and approach their peak in the next few days. More below on this. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Issued at 300 AM MDT Fri Jun 7 2024 With plenty of moisture to work with and a front dropping through eastern Utah and western Colorado, look for showers and storms to linger well into overnight hours Saturday into Sunday, before finally tapering off. Subtropical moisture continues to pump into the Four Corners region through the weekend, as clockwise flow around the high now located over the Gulf Coast draws it northward. PWATs peak around 150-200% of normal for Sunday and Monday. By Sunday morning, the low that had been lurking off the coast of Baja California will have made its way into Arizona, now as an open wave. This will provide some extra dynamic lift during the afternoon and evening hours Sunday, on top of typical diurnal heating acting on the terrain. With the extra moisture and lift, look for more widespread shower and thunderstorm activity, beginning over the higher terrain early in the afternoon and then spreading across the valleys. The main threat will remain gusty outflow winds, as surface levels will still be rather dry, but as the day wears on, chances for moderate or even brief heavy rain will increase. What`s left of the Baja low will be east of the Divide by Monday morning, leading to a downturn in shower and storm coverage over the lower elevations. With plenty of moisture to work with but only diurnal heating to use a source of lift, look for convection to favor the higher terrain, especially along the Divide. A trough passing by to the north during this period may drag a front through the northern half of the CWA, providing a focus for some more intense activity, but which will be out of the area by Monday evening. The trough moving across the Northern Rockies on Monday evening is actual the remnant of a larger Pacific trough that had moved onshore late Sunday and split. The northern packet of energy is to become this trough, while the southern packet of energy drifts south to the coast of Baja and becomes yet another cutoff low pressure. As this low drifts slowly over the eastern Pacific and the northern stream trough and its associate front sweeps through, ridging once again tries to build into the Desert Southwest for Tuesday. This will mean a general drying trend with diminishing convective coverage and increasing temperatures for the remainder of the week. As far as temperatures are concerned, Sunday and Monday will see temperatures around 3 to 5 degrees above normal, with Monday being the coolest day of the period. As the atmosphere dries out and warm high pressure reasserts itself over the Desert Southwest, look for a warming trend from Tuesday onward, back up to around 10 degrees above normal for most locations. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1114 PM MDT Thu Jun 6 2024 VFR conditions and light winds will occur through late morning on Friday. Afternoon breezes and the chance of passing thunderstorm will increase through the afternoon at most TAF sites. Confidence remains low on direct impacts to the airfield due to isolated storm coverage. Gusty winds will be the main threat and may occur from outflow from distant storms. The probability of below VFR remain very low however. && .HYDROLOGY... Issued at 229 PM MDT Tue Jun 4 2024 High pressure building overhead through the end of the week will result in an unseasonably warm period across the Western Slope. Simultaneously, as those temperatures rise, so will the rate of snowmelt across our high terrain. Even though low to mid elevations have already melted out, there`s still an abnormally high amount of snow left over basins generally at and above 11,000 ft...and it`s melting...fast. As a result, creeks, streams and major tributaries along the Upper Colorado River Basin are on the rise. Seasonal peak flows are expected over the next 10 days, with the Upper Gunnison, Upper Yampa and Colorado Headwaters basins likely peaking for the season this weekend. Current guidance oscillates diurnal peaks cresting the Action Stage for portions of Gore Creek and Eagle River in Eagle County. No highlights needed, yet, for that area after discussion with local officials but we will keep an eye on things over the coming days. The Elk River near Milner in Routt County, on the other hand, is expected to exceed Minor Flood Stage each morning through Sunday. This increase in forecast stage/flow warranted an upgrade from Flood Advisory to a Flood Warning. Also, the East River near Almont is forecast to exceed Action Stage each morning through Sunday, with the potential for exceeding Flood Stage by Saturday. For now, a Flood Advisory is in effect for this stretch of river. However, stay tuned for the potential upgrade to a warning and/or extending the advisory downstream into the Gunnison at Gunnison. As scorching temperatures lure folks to the water, please remember the potential hazards associated with high flows during the snowmelt season. Fast flows are not just dangerous for those choosing to float the rivers. In addition, high diurnal swings may drastically change the depth and flow for normally small creeks and streams. Swift currents and cold water temperatures can catch you off guard, so please be vigilant with current conditions and look for forecast updates when recreating or working near the water`s edge. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...15 LONG TERM...BGB AVIATION...TGJT HYDROLOGY...ERW